This invention relates generally to aviation equipment and, in particular, to aviation lights.
Dual-color anti-collision lights (ACLs) are used in numerous aviation applications, including the Royal Air Force, Australian, New Zealand, and United States Air Forces as well as numerous civilian applications. Typically, dual-color ACLs incorporate a white strobe having an effective luminescence of 1500-2500 cd for daytime operations and a red strobe having effective luminescence of 150-250 cd for nighttime operations. According to federal regulations and various international agreements, the chromaticity of the white strobe must meet the definition of “Aviation White” as defined, among other places, in Federal Acquisition Regulations (FAR) 25.1397. Similarly, the chromaticity of the red strobe must meet the definition of “Aviation Red” as defined by FAR 25.1397.
Conventional dual-color ACLs employ xenon flash tubes to provide the desired light output and chromaticity. A first xenon flash tube is positioned at the focus of a reflector positioned behind a clear lens to provide the white strobe output. A second xenon flash tube is positioned at the focus of a reflector positioned behind a red filter. Conventional dual-color ACLs have a limited operational life, require a comparatively heavy high-voltage power supply to operate the flash tubes, and must contain two separate optical systems, one each for the white and red strobes.
Light Emitting Diodes (LEDs) offer the advantage of improving reliability, reducing power consumption, and reducing the weight of a dual-color ACL. Achieving the desired effective luminescence, however, requires the use of multiple relatively costly LEDs in place of a single xenon flash tube. Moreover, it is well known that white LEDs, which use a phosphor conversion to convert light output from a blue LED die into white light, exhibit a color shift with age and temperature. The effect is to cause the white LEDs to produce light that is more greenish as the phosphor deteriorates. As a result, a white LED that initially has a chromaticity within the definition of Aviation White may, over time, color shift so that it is no longer in compliance with applicable regulations.